Sheet materials such as paper, metal foil, and the like are often rolled in coils on hollow cores for storage and handling. In the can industry, for example, aluminum sheet material is manufactured and rolled in coils on metal cores at one site and then shipped to another site for uncoiling in the manufacture of cans. Rolls of paper of the type suitable for use as newsprint are manufactured and shipped in the same manner.
Such rolls can be quite heavy and difficult to handle: and this handling can partially collapse or deform the cores. Before the rolls can be handled further or mounted on a support arbor, the cores must be reopened and substantially restored to their original shape. This is typically done by inserting an expandable tool into the core.
Several such expansion tools have been developed for this purpose. Tools representative of the prior art are shown in U.S. Pat. Nos. 3,749,365; 3,677,058; 3,635,440; 3,625,046; and 3,618,895 to Van Gompel as well as U.S. Pat. No. 3,292,903 to Meyer and U.S. Pat. No. 4,155,242 to Peterson. However, these devices are not capable of withstanding the tremendous pressures, sometimes upwards of twenty-five tons, that are brought to bear upon the jaws and tongue of the expansion device.
U.S. Pat. No. 2,643,562 (Geddes, 1953) discloses a spreading tool designed primarily for reshaping deformed automobile bodies. This reference discloses a linkage means to expand the jaws of the tool.
U.S. Pat. No. 1,932,584 (Hanson, 1933) suggests the use of a wedge-shaped slide to actuate the jaws outward, though the apparatus in Hanson is designed for exerting only minimal outward force which is necessary for reshaping a can.
Rollers have also been developed for transferring the expansion force of the tongue or spreading fork to the deformed roll. However, at high pressures the rollers are subject to frequent breakage. Metal bearing surfaces have also not worked well at high pressures as the tongue adheres to the metal jaws at the high pressures developed at the wedge/tongue interface as are necessary for the tasks for which the tool is designed. Metallic wedges used to date have suffered the same problem. Further, metal rollers, bearings and wedges require complicated means of attachment to the jaws which themselves break and/or require time and skill in replacing when any element of the pressure transference system needs to be accessed or removed.
A long-felt commercial need thus exists for an improved core expander tool with a durable, replaceable, maintenancefree wedge having a bearing surface capable of transferring expansion forces of over 3,000 pounds or more from the tongue through the jaws to the core and of releasing and forcing back the tongue after each use during multiple core reforming operations, all without breakage or binding.